Page 56 - A Guide to MATLAB for Beginners and Experienced Users

M-Files 37

Script M-Files
We now show how to construct a script M-file to solve the mathematical prob-
lem described earlier. Create a file containing the following lines:
format long
x = [0.1, 0.01, 0.001];
y = sin(x)./x
We will assume that you have saved this file with the name task1.m in your
working directory, or in some directory on your path. You can name the file
any way you like (subject to the usual naming restrictions on your operating
system), but the “.m” suffix is mandatory.
You can tell MATLAB to run (or execute) this script by typing task1 in
the Command Window. (You must not type the “.m” extension here; MATLAB
automatically adds it when searching for M-files.) The output — but not the
commands that produce them — will be displayed in the Command Window.
Now the sequence of commands can easily be changed by modifying the M-file
task1.m. For example, if you also wishto calculate sin(0.0001)/0.0001, you
can modify the M-file to read

format long
x = [0.1, 0.01, 0.001, 0.0001];
y = sin(x)./x
and then run the modified script by typing task1. Be sure to save your
changes to task1.m first; otherwise, MATLAB will not recognize them. Any
variables that are set by the running of a script M-file will persist exactly
as if you had typed them into the Command Window directly. For example,
the program above will cause all future numerical output to be displayed
with15 digits. To revert to 5-digit format, you would have to type format
short.

Echoing Commands. As mentioned above, the commands in a script M-file
will not automatically be displayed in the Command Window. If you want the
commands to be displayed along withthe results, use echo:

echo on
format long
x = [0.1, 0.01, 0.001];
y = sin(x)./x
echo off